"Une mère, un mari, un mariage" (One mother, one husband, one marriage): This is the call to arms for those opposed to the legalization of gay marriage and gay adoption in France.

Under this banner thousands turned out on Saturday for demonstrations organized in every one of France's 96 regions.

The French parliament adopted Saturday the main clause of a bill that would allow same-sex marriage and grant gay couples the right to adopt children.

Deputies voted 249-97 to back the clause.

About 1,000 people holding signs that read, "We are all born of a man and a woman" gathered in Paris not far from the parliament building, Reuters reported. Protesters also assembled outside the town hall in Lyon.

The umbrella group for the anti camp is called "manif pour tous" (a pun: manif, or demonstration, for everyone as opposed to marriage for everyone). Spokesman Tugdual Derville said it would be a symbolic day, illustrating that opponents "are present everywhere in France."

The group was behind a huge rally in Paris attended by between 340,000 and 800,000 people on Jan. 13. Saturday's event, according to Derville, is for those who want to demonstrate but perhaps do not have the means to travel to Paris.

So what exactly are they protesting against?

They insist their movement is not homophobic, that it is the legalization of gay adoption that they are against as this amounts to the breakdown of the traditional family.

They say children have a fundamental right to have a father and a mother.

"We must think of future generations. Not only of the desires of adults today," Derville told NBC News.

But those in favor have vocal support, too.

"Marriage should be a simple contract between two individuals. Let's make it available to all couples eager to make this contract to each other," Christophe Barbier, editor of the influential L'Express weekly news magazine and a supporter of the law, told NBC News.

The opponents, Barbier believes, are "afraid that after civil contracts (between homosexual couples), and now marriage, the next step will be IVF (for lesbian couples) and surrogate pregnancies (for gay men)."

President's pledgeOther countries in Western Europe -- such as Belgium and the Netherlands -- have already legalized gay marriage. But nowhere has the opposition been as vocal as in France -- not even in Spain and Portugal, which are predominantly Catholic like France.

This opposition may seem at odds with France's 'liberal' reputation. But Barbier insisted to NBC News: "France is not liberal, neither economically nor socially. France is conservative -- and occasionally revolutionary."

President Francois Hollande was confident the legislation would pass thanks to his Socialist Party's majority. Legalizing gay marriage was a manifesto pledge during his 2012 election campaign.

According to Barbier, for political reasons the president had to fulfill this pledge: "Francois Hollande needs to deliver on the promises made during his campaign: In the economic field, this is difficult, with social issues, it's easier."

Luckily for him, he also appears to have the backing of the majority of French voters.

A recent poll for Atlantico.fr carried out by Ifop found that 63 percent of people in France support the legalization of same-sex marriage. Forty-nine percent supported gay adoption.

This does not diminish the fervor of those opposed. According to a poll cited by "Manif pour Tous" only 6 percent of people see this issue as a priority.

"The priority is the economy, housing and jobs, so politically the president should have the wisdom to renounce this project," said Derville, the group's spokesman.

A poll by Yougov for Le Huffpost (the Huffington Post's French-language edition) backs this up, finding 72 percent feel the debate has already gone on for too long.

Unfortunately for them, the real debate in France's National Assembly just started on Tuesday and is due to run for two whole weeks -- including weekends.